Rav Arama writes that after the sending of Haman’s original decree, Jews likely went into hiding. At this point, they now felt confident to come back into the cities, and reestablishing their economical and social infrastructure there, making the cities their own again.
ט וְנָתוֹן הַלְּבוּשׁ וְהַסּוּס עַל–יַד–אִישׁ מִשָּׂרֵי הַמֶּלֶךְ הַפַּרְתְּמִים וְהִלְבִּישׁוּ אֶת–הָאִישׁ אֲשֶׁר הַמֶּלֶךְ חָפֵץ בִּֽיקָרוֹ וְהִרְכִּיבֻהוּ עַל–הַסּוּס בִּרְחוֹב הָעִיר וְקָרְאוּ לְפָנָיו כׇּכָה יֵעָשֶׂה לָאִישׁ אֲשֶׁר הַמֶּלֶךְ חָפֵץ בִּיקָרוֹ
9. “And the clothes and the horse should be given through a man from the officers of the king. And the man whom the king desires to honor should be dressed. And they should ride him on the horse in the street of the city. And they should call out before him, ‘Like such is done to the man whom the king desires to honor.’”
- Rav Arama writes that Haman advises the need for a proclamation because he anticipated that Achashverosh might otherwise become jealous. He therefore wanted it to be clear that this honor was coming from the king, who had the power to give honor.